=over

=item study SCALAR
X<study>

=item study

At this time, C<study> does nothing. This may change in the future.

Prior to Perl version 5.16, it would create an inverted index of all characters
that occurred in the given SCALAR (or L<C<$_>|perlvar/$_> if unspecified). When
matching a pattern, the rarest character from the pattern would be looked up in
this index. Rarity was based on some static frequency tables constructed from
some C programs and English text.

=back